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  <script>
    // let arr = [10, 20, 30, 40, 50]
    // console.log(arr)
    // console.log(arr[4])

    let arr = ['星期一', '星期二', '星期三', '星期四', '星期五', '星期六', '星期日']
    console.log(arr[6]);
    console.log(arr.length);

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